The present invention relates to a power transmitting apparatus with a torque converter in which a lockup clutch having a damper is provided, and more particularly to the apparatus capable of reducing a vibration at a time of engaging a lockup clutch.
Conventionally, the torque converter is mounted on the power transmitting apparatus having an automatic transmission for transmitting a power of an engine to the automatic transmission. In order to reduce a power loss of the torque converter and improve a specific fuel consumption performance of a vehicle, there is employed a structure in which a directly-coupled clutch, namely, the lockup clutch is assembled in the torque converter so as to directly connect an input shaft of the automatic transmission to a crank shaft.
As the automatic transmission, there are normal automatic transmissions (hereinafter, referred to as AT) having a planetary gear or the like and an automated manual transmission (hereinafter, referred to as AMT) having a plurality of transmission gear trains. The AMT is based on the structure of a manual type transmission, and includes an input shaft which is connected to an engine and to which a plurality of drive gears are attached, and an output shaft which is connected to drive wheels and to which a plurality of driven gears are attached in engaging with the drive gears to form transmission gear trains. The transmission gear trains are automatically switched by a hydraulically driven actuator according to a traveling state.
In both types of the automatic transmissions, when assembling the lockup clutch in the torque converter, a torsion damper, namely, a damper spring is attached to the lockup clutch in order to absorb a rotational fluctuation of an engine. When traveling in a state of engaging the lockup clutch, vibrations are usually transmitted to a vehicle body via the automatic transmission due to the rotational fluctuation of the engine. The vibration transmitting system at the time of engaging the lockup clutch is considered to be caused by following four elements; {circle around (1)} an inertia moment of rotating components at an upstream side of the torsion damper in a power transmitting path, namely, the inertia moment thereof at the engine side; {circle around (2)} an inertia moment of the rotational components at a downstream side of the torsion damper, namely, at the side of the automatic transmission; {circle around (3)} a torsional rigidity of the torsion damper connecting the both sides; and {circle around (4)} a torsional rigidity of the input shaft in the automatic transmission connecting with the vehicle body. In this vibration transmitting system, there are a primary resonance point in which the inertia moment at the upstream side and the inertia moment at the downstream side vibrate with the same phase, and a secondary resonance point in which those moments vibrate in reverse phases, respectively.
Japanese Patent No. 2836319 discloses a structure that an inertial mass is provided at the upstream side of the torsion damper within the torque converter, namely, at the engine side, in order to reduce a primary vibration, so that the inertia moment at the engine side is increased. However, when traveling in an engaging state of the lockup clutch, not only the primary resonance point but also the secondary resonance point is generated as mentioned above, where the inertia moments at the both upstream and downstream sides vibrate in the reverse phases. On the assumption that the secondary resonance is 30 Hz in a 4-cylinder engine, the rotational fluctuation is generated due to two explosions per one rotation, and thus an engine speed of the secondary resonance point is expressed by 30xc3x9760/2=900 rpm. When engaging the lockup clutch with the engine speed equal to or more than 1200 rpm or more, the secondary resonance point is very close to a range for practical use, so that there may occur a low-frequency sound or vibrations.
As a method of lowering the secondary resonance point, it is considered to reduce the torsional rigidity of the torsion damper and the input shaft, and also optimize a distribution of the inertia moments between the upstream side of the torsion damper and the downstream side thereof. Although the Japanese Patent as described above is available for lowering the primary resonance point since the inertial mass is provided at the upstream side of the torsion damper, it is impossible to lower the secondary resonance point. Accordingly, the conventional method can not prevent the low-frequency sound from being transmitted into a passenger""s compartment.
An object of the present invention is to reduce low-frequency sounds or vibrations occurred in a power transmitting system of a power transmitting apparatus with a torque converter.
In accordance with the present invention, there is provided a power transmitting apparatus with a torque converter comprising a torque converter provided with a pump impeller connected to a crank shaft of an engine and a turbine runner opposing to the pump impeller, and a lockup clutch assembled within the torque converter with a torsion damper and connected to an input shaft of a transmission, wherein an inertial mass is provided at a downstream side of the torsion damper.
In accordance with the present invention, there is further provided the power transmitting apparatus with the torque converter comprising the torque converter provided with the pump impeller connected to the crank shaft of the engine and the turbine runner opposing to the pump impeller, and the lockup clutch assembled within the torque converter with the torsion damper and connected to then input shaft of the transmission, wherein an input clutch engaging and disengaging the turbine runner with the input shaft is provided between the turbine runner and the input shaft, and the inertial mass is provided in the input clutch.
The inertial mass of the present invention may be provided at an outer peripheral side of the input clutch, or may be formed by increasing a thickness of structuring elements of the torque converter or the transmission.
According to the present invention, the inertial mass functioning as a flywheel is provided at the downstream side of the torsion damper provided in the lockup clutch of the torque converter in the power transmitting path, thereby the inertia moment at the downstream side can come closer to the inertia moment at the upstream side, so that the secondary resonance point in the power transmitting system can be lowered. As an effect thereof, the low-frequency sound and the vibration transmitted within the passenger""s compartment can be reduced.
Further, since the secondary resonance point is lowered, it is possible to expand the lockup area to a low speed and high load area, so that fuel consumption can be improved.